Hizbul Mujahideen, also spelled Hizb-ul-Mujahidin (transl. 'Party of Holy Fighters'), is a Pakistan-based Islamist militant organisation that has been engaged in the Kashmir insurgency since 1989. It aims to separate Kashmir from India and merge it with Pakistan, and is thus one of the most important players in the region as it evolved the narrative of the Kashmir conflict by steering the struggle away from nationalism and towards jihadism.

Founded in September 1989 as an umbrella group of Islamist militants, Hizbul Mujahideen quickly came under the control of Jamaat-e-Islami Kashmir; it is considered to be the military wing of the organisation. It was supported, since its inception, by Pakistan's Inter-Services Intelligence and was established through an effort initiated under erstwhile Pakistani president Muhammad Zia-ul-Haq. It is headquartered in Muzaffarabad, the capital of Pakistani-administered Azad Kashmir, and also has liaison offices in Islamabad and Rawalpindi, Pakistan's political and military capital cities, respectively.

The organisation has claimed responsibility for multiple armed attacks in Kashmir. It has been designated as a terrorist group by the European Union, India, Canada, and the United States. It remains a lawfully-operating organisation in Pakistan.

The efforts for the creation of the Hizbul Mujahideen go back to 1980, when Pakistani President Zia ul-Haq called the chief of Jamaat-e-Islami in Azad Kashmir, Maulana Abdul Bari, and asked for assistance in raising an insurgency in Indian-administered Kashmir. Zia said that he would be able to divert funds and resources from the Afghan mujahideen for a conflict in Kashmir. Bari travelled to the Kashmir Valley and met with the leaders of Jamaat-e-Islami Kashmir. Protracted negotiations continued for three years when finally, the founding amir of the Jamaat-e-Islami Kashmir, Maulana Saaduddin Tarabali, was invited for a meeting with Zia ul-Haq in May 1983. Saaduddin wanted complete operational control of the insurgency, with Pakistan's role limited to military training and financial support. Pakistan agreed albeit reluctantly, and a deal was struck. Maulana Saaduddin sent his own son as part of the first group of volunteers for military training.

However, the progress with Jamaat-e-Islami was sluggish. The ISI got frustrated with it and started looking for other options. It made contact with Jammu and Kashmir Liberation Front (JKLF) in 1984 and struck a deal with it in 1986. According to scholars, JKLF was only a short-term expedient for ISI, a means to spur Jamaat-e-Islami into action. Some 10,000 militants were trained by July 1988, operating in fifty units, when an insurgency was launched. Operating under the JKLF banner were also a number of Islamist jihadi groups that owed loyalty to Jamaat-e-Islami: a group called "Zia Tigers" operating since 1987, "Al-Hamza" since 1988, "Hizbul Ansar" led by Muzaffar Shah, a largest and best organized group called "Ansarul Islam", and a subsidiary of it called "Al-Badr". According to Arif Jamal, "this vast network of jihadi groups worked within the JKLF for many months; they were among the most active members of the insurgency."

In August 1989, the Jamaat-e-Islami of Azad Kashmir sent a commander called Masood Sarfraz to bring the various Islamist groups together and create a serious organisation parallel to the JKLF. "Hizbul Mujahideen" ("Party of holy warriors") was his chosen name for the new umbrella group. While his efforts were under way, Ansarul Islam, which was under pressure from the Indian security forces, had also changed its name to "Hizbul Mujahideen". The two organisations operated in parallel for a few weeks, but merged in October 1989. Muhammad Ahsan Dar was chosen as the leader of the united group in this meeting, but Hilal Ahmed Mir (alias Nasirul Islam) of the former Ansarul Islam is said to have been elected as its amir later.

The launch of insurgency by JKLF in July 1988 alerted the members of the Jamaat-e-Islami Kashmir to the fact that "a new game has started". Informal relationships with the militant groups were strengthened, with various Jamaat members taking direct roles. The senior leadership of the Jamaat did not get involved, except for Syed Ali Shah Geelani, who worked with Muhammad Ahsan Dar in his personal capacity.

The ISI and the Jamaat-e-Islami of Azad Kashmir were intent on bringing Hizbul Mujahideen under the control of Jamaat-e-Islami Kashmir. A meeting was arranged in Kathmandu on 14 January 1990, with participants from the Jamaat organisations from Pakistan, Azad Kashmir and the Kashmir Valley. The Kashmiri Jamaat was resistant to direct involvement in the insurgency, saying that it would destroy the organisation and open it to Indian assault. But Syed Ali Shah Geelani dramatically appeared when the negotiations stalled and pushed the Jamaat into supporting the insurgency. Having decided to participate in the militancy, states Arif Jamal, the Jamaat-e-Islami Kashmir moved to "decisive action, activating a decade of planning".